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CHEMICAL REACTIONS

CHEMICAL REACTIONS. Reactants: Zn + I 2. Product: Zn I 2. Chemical Equations. Depict the kind of reactants and products and their relative amounts in a reaction. 4 Al (s) + 3 O 2 (g) ---> 2 Al 2 O 3 (s) Numbers in the front : coefficients- amount of molecules or ions

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CHEMICAL REACTIONS

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  1. CHEMICAL REACTIONS Reactants: Zn + I2 Product: Zn I2

  2. Chemical Equations Depict the kind of reactants and products and their relative amounts in a reaction. 4Al (s) + 3O2 (g) ---> 2Al2O3 (s) Numbers in the front : coefficients- amount of molecules or ions The letters (s), (g), and (l) are the physical states of compounds.

  3. Introduction Chemical reactions occur when bonds between the outermost parts of atoms are formed or broken Chemical reactions involve chemical change making new materials with new properties + energy changes. Symbols represent elements Formulas describe compounds Chemical equations describe a chemical reaction

  4. The charcoal used in a grill is basically carbon (C). The carbon reacts with oxygen to yield carbon dioxide. C + O2 CO2 This reaction is a concise sentence that also is quantitative.

  5. Conservation of Matter During a chemical change mass is conserved, or remains the same. All the atoms are still present, but in a different arrangement. Lavoisier, 1788

  6. Balancing Equations Once theformulas are written correctly…….do NOT change the subscripts!!!! *changing the subscript changes the compound* NaCl is not Na2Cl2 H2O is not H2O2 Coefficients are added in front of the formula indicates the amount that is present--- this satisfies the Law of Conservation of Matter

  7. Subscripts vs. Coefficients • The subscripts tell you how many atoms of a particular element are in a compound. The coefficient tells you about the quantity, or number, of molecules of the compound.

  8. Chemical Equations 4 Al(s) + 3 O2(g) ---> 2 Al2O3(s) This equation means: 4 Al atoms + 3 O2 molecules ---produces---> 2 molecules of Al2O3AND/OR 4 moles of Al + 3 moles of O2 ---produces---> 2 moles of Al2O3

  9. Steps to Balancing Equations • Write the correct formula for the reactants and the products. DO NOT TRY TO BALANCE IT YET! • Do an Atom Inventory • Use coefficients in front of formulas to balance the reaction • Check your answer to see if: The numbers of atoms on both sides of the equation are now balanced. The coefficients are in the lowest possible whole number ratios. (reduced)

  10. Some Suggestions to Help You Take ONE element at a time work from left to right leave H and O until the end If everything balances except O with a whole # ….2x the coefficients Polyatomic ions that are on both sides of the equation should be kept together in the atom inventory If H2O is on one side of the equation and OH-1is on the other, write H2O as HOH

  11. Balancing Equations ___ Al(s) + ___ Br2(l) ---> ___ Al2Br6(s) 2 3

  12. Balancing Equations ____C3H8(g) + _____ O2(g) ----> _____CO2(g) + _____ H2O(g) ____B4H10(g) + _____ O2(g) ----> ___ B2O3(g) + _____ H2O(g)

  13. Balancing Equations Sodium phosphate + iron (III) oxide  sodium oxide + iron (III) phosphate Na3PO4 + Fe2O3 ----> Na2O + FePO4

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